This invention relates to slicing machines that are principally used for slicing food products, particularly for slicing cheese, meat and pressed or moulded meat products.
Such a slicing machine comprises a rotating blade which either has a spiral cutting edge or has a circular cutting edge and is mounted for planetary motion, and means to feed the product towards the blade so that upon each revolution or each gyration of the blade, a slice is cut from the face of the product. The means to feed the product may be a continuous conveyor but usually the slicer includes a fixed platform on which the product is placed, and a feeding head which engages the rear face of the product and which urges it product towards the blade. The feeding head may be moved by a hydraulic ram or by a leadscrew driven by a stepping or variable speed electric motor.
The product may be moved forwards at a constant speed so that upon each revolution or each gyration of the blade a slice is cut from its face. Typically the feeding head is moved continuously to cut relatively thin slices of, for example ham or sausage. Alternatively, the piece of meat or meat product is moved forward by the feeding head stepwise each time the cutting edge of the blade is away from the product. This is typically used where thicker slices are required, for example when slicing corned beef.
Such slicing machines usually include a physical abutment to prevent the feeding head being moved forwards beyond a predetermined point and so prevent the feeding head from being brought into contact with the cutting edge of the blade. In addition to this they also include an end stop detector which detects the presence of the feeding head upstream from the physical abutment and emits a signal to stop the further forwards movement of the feeding head and return it to its starting position remote from the cutting blade. The end stop detector and the physical abutment are normally placed close together in the feeding direction so that as much of the block of product is cut as possible thereby to reduce waste. Typically the physical abutment and the end stop detector are a distance corresponding to only one, or at most two thin slices apart so that the maximum number of slices are cut from each block of product. However, when the slicing machine is cutting thick slices from a block of product it is possible for a further stepwise feed of the feeding head to be initiated when the feeding head is still upstream from the end stop detector but this further feeding step results in the feeding head hitting the physical abutment at high speed which can result in damage to the slicer. Whilst the presence of the feeding head is detected by the end stop detector the movement of the feeding head overruns and hits the physical abutment before the movement of the feeding head is disabled and before the feeding head is returned to its start position remote from the blade.
When the feeding head passes the end stop detector the forwards movement of the feeding head is stopped and the head is returned to its starting position, the slicing machine is usually part of the way through cutting a slice from the front face of the block of product. In this case the slice that is being sliced is destroyed as the remaining portion of the block of meat or meat product is moved away from the blade.
Usually the slicing machine, has a jump conveyor associated with it, the jump conveyor is arranged to produce groups of slices. After a predetermined number of slices have been cut and have fallen onto the jump conveyor its speed is increased for a short period of time. This provides a gap between the last slice of a preceding group and the first slice of a following group. This change in speed of the jump conveyor downstream of the blade is usually instigated and reset by the signal from the end stop detector so that, when the feeding head reaches the end of its travel a jump sequence of the jump conveyor is initiated. However, when this occurs at a time at which the last slice of a particular group has not been cut the leading slice in the part group of slices so formed is located at a different position on the jump conveyor from that normally occupied by a complete group of slices and this leads to the part group often being incorrectly discharged from the jump conveyor and results in further dislocation and possible damage to the slices of product.